The Classical epic form has many elements that comprise the tradition. Among these many elements are descriptions of wars, lists of armies, settings that alternate between natural and supernatural. Milton uses these particular ones and many more as he blends Classical traditional with his Jacobean period Christian epic (1667).
Of special interest is the way Milton uses Classical alternation of setting. This permits a unique view of an ancient Biblical story about the fall of angels from Heaven. The first striking scene is of Lucifer and his followers falling literally into Hell. Other scenes introduce Adam and Eve on a paradisaical Earth. Other scenes reveal conversations in Heaven. With these Classical tradition alternations, we see the perspectives of three separate points of view and the activities of three separate groups of entities, including the activity of the classically inspired games that test strength that are played out in Hell that are reminiscent of the games played in Homer's Iliad.
Heroick deem'd chief mastery to dissect
With long and tedious havock fabled knights
In battles feign'd; the better fortitude
Of patience and heroick martyrdom
Unsung; or to describe races and games,
Or tilting furniture, imblazon'd shields,
Impresses quaint, caparisons and steeds,
Another Classical epic form of alternation used by Milton is that of alternating between narration, description and dialogue. You can see that, for example, in the conversations between Satan and his fallen followers and in the conversations between Adam and Eve: each of the three elements--narration, description, dialogue--keeps their alternating place in Milton's epic. One other Classical element of special interest to note is the motif of the repeated query "what cause?" This illustrates a Classical form that employs a repeated thematic question to emphasize a thematically important aspect of the epic.
Say first—for Heaven hides nothing from thy view,
Nor the deep tract of Hell—say first what cause
Moved our grand parents, in that happy state,
Favoured of Heaven so highly, to fall off
From their Creator, and transgress his will
For one restraint, lords of the World besides. (Book I)
Led on, yet sinless, with desire to know
What nearer might concern him, how this world
Of Heaven and Earth conspicuous first began;
When, and whereof created; for what cause;
What within Eden, or without, was done
Before his memory; as one whose drouth
Yet scarce allayed still eyes the current stream,... (Book IX)